The Philosophical magazine; a journal of theoretical, experimental and applied physics . aratus in whichthey should be so separated as to render this less easy. The form of apparatus which I finally adopted is shown insection in fig. 1. The tube (a b c)containing two small porous bat-tery-pots {gf), the graphite elec-trode, and the mercuric iodide tobe electrolyzed, is U-shaped, andthe two branches are connectedby a constricted portion (c), whichfurther materially hinders themixng of the fused products ofdecomposition in the two branchesof the tube. This apparatuspasses through a hole in the t
The Philosophical magazine; a journal of theoretical, experimental and applied physics . aratus in whichthey should be so separated as to render this less easy. The form of apparatus which I finally adopted is shown insection in fig. 1. The tube (a b c)containing two small porous bat-tery-pots {gf), the graphite elec-trode, and the mercuric iodide tobe electrolyzed, is U-shaped, andthe two branches are connectedby a constricted portion (c), whichfurther materially hinders themixng of the fused products ofdecomposition in the two branchesof the tube. This apparatuspasses through a hole in the tincover (Ji) which supports it, anddips into the oil in the beake*,which is heated to the desiredtemperature by means of a gas-flame or sand-bath, at which it iskept constant Ijy placing thebulb of the air-thermometer (Ji)in communication with a gas-regulator. When mercuric iodideis electrolyzed in such an appa-ratus with a current of about 002ampere, iodine is liberated at temperatures far above the melting-point of the the current was too stiong the circuit was usually. DEL of Electrolytic Decomposition. 43 broken, apparently in consequence of the heat generatedat the + electrode volatilizing, or otherwise causing themercuric iodide to disappear from the porous pot. Afterpassing the current for some hours the gas was extinguished,and when the apparatus had become cool the two branches ofthe U-tube were cut asunder and broken open for the + branch, both within and without the porous pot,mercuric iodide and black feathery streaks of iodine werefound which gave the starch reaction, and the upper part ofthe glass tube was coated with volatilized iodine. Iodine dissolves freely in fused mercuric iodide, producingbut little change in the colour of the latter ; but just as soli-dification commences, more or less complete separation seemsto take place with the formation of these black patches richin iodine (and Hg^Ig ?) and an evolution of iodine
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